The present invention relates to hobs of the type which employ radiant heating elements, and heating units therefor.
It is desirable that the heat output of a hob responds quickly to the setting control. This is one reason for the popularity of gas appliances where the change in heat output occurs substantially simultaneously with the change in setting. With regard to electric hobs, this desire for a quick response time has resulted in the gradual trend, initially from solid plate to spiral elements, and more recently to hobs comprising a glass-ceramic top plate, commonly referred to as ceramic hobs, using radiant heating elements, such as tungsten halogen lamps, or inductive heating units. Apart from a quick response time over conventional solid plate and spiral type hobs, ceramic hobs also give the advantage of being easy to clean and are aesthetically pleasing, normally comprising four or more heating units mounted under a single sheet of glass-ceramic.
In order to provide at least one hotplate surface in an otherwise conventional solid plate hob with the rapid response time afforded by glass-ceramic hobs, it has been proposed by the present inventors to produce glass-ceramic "drop-in" units which could be substituted for one or more of the solid plate elements. This is disclosed in UK Patent Nos. GB 2177578B and GB 2138935B.